The invention relates to a headlight, particularly a vehicle headlight, having a light source disposed in front of a reflector, and having a fiber-optic waveguide. As an elongated light decoupling element which, at least in areas, is adjacent to an edge of the reflector, the waveguide is constructed with a light exiting surface facing away from the reflector.
From European Patent document EP 0 900 694 A2 and from German Patent Document DE 100 40 302 A1, vehicle headlights are known, which have a light source for generating the light of a headlight. For example, FIG. 6 shows a front perspective view of a set of headlights as might appear on one side of the front of a vehicle, and FIG. 7 shows a front perspective view of a single headlight with a reflector and a light source in the center. The light source is disposed in front of a reflector. The known headlights have a fiber-optic waveguide which, as an elongated light decoupling element, is adjacent, at least in areas, to an edge of the reflector.
In the case of the known vehicle headlights, a light source disposed in front of the reflector generates the light of a headlight, such as daytime driving light or low-beam light or high-beam light. By way of a second light source, light is coupled into the fiber-optic waveguide, which light is emitted or decoupled as a signaling light.
As a result of the coupling-in by way of the faces of the fiber-optic waveguide or by way of special coupling-in elements, relatively high losses of light occur so that, although the fiber-optic waveguide is suitable for generating a signalling light, the emitted light does not have a sufficient intensity for a use as a daytime driving light or a low-beam light, and has a relatively inhomogeneous and undesirable light intensity distribution. While a relatively undirected light distribution is not necessarily a disadvantage for a signalling light, relatively high demands are made on the light of a headlight, for example, a low-beam light or daytime driving light, with respect to a homogeneous luminance and a directed light distribution.
It is therefore an object of the present invention to improve the known headlights with the decoupling of light by way of an elongated fiber-optic waveguide such that a homogenous luminance of a high light intensity with a formable or directed light distribution is permitted, as required, for example, for generating a daytime driving light.
This object is achieved according to the invention by providing a headlight, particularly a vehicle headlight, having a light source disposed in front of a reflector, and having a fiber-optic waveguide which, as an elongated light decoupling element which, at least in areas, is adjacent to an edge of the reflector, is constructed with a light exiting surface facing away from the reflector. The interior side of the reflector facing the light source is, at least in areas, constructed such that it forms a first focal point at the site of the light source and reflects light emitted from the light source to a light entering surface of the light decoupling element, which light entering surface faces away from the light exiting surface.
The light of the light source is guided from the reflector to the light entering surface of the fiber-optic waveguide or the light decoupling element, so that the fiber-optic waveguide is virtually transilluminated along its entire length. The relatively high optical losses as a result of the coupling-in, the propagation, and the deflection, are thereby virtually eliminated or are considerably reduced. In addition, as a result of the uniform light distribution on the back side or the light entering surface of the fiber-optic waveguide, a reduction of the light intensity because of a temperature-limited coupling-in is avoided. Thus, a high light intensity can be achieved with a formable and homogeneous light distribution. This achieves the high efficiency which is important for the daytime driving light or the low beam light or the high beam light.
According to a preferred embodiment of the invention, the interior side of the reflector is constructed as a section of a rotational solid whose contour is a result of a rotation about a headlight axis of an ellipse set in the beaming direction with respect to a headlight axis at an angle of less than 90°, whose first focal point F1 is arranged at the site of the light source and whose second focal point F2 is arranged adjacent to the light entering surface of the light decoupling element and, because of the rotation, forms a ring-shaped focal line. In this case, the fiber-optic waveguide expediently has a ring-shaped construction.
Thus, all light of the light source or of the reflector is guided in a targeted manner to the light entering surface of the fiber-optic waveguide. By way of the light entering surface, the light can couple into the fiber-optic waveguide and, in a correspondingly directed manner, can exit again from the light exiting surface. This contributes to a further increase of the efficiency of the headlight. By a corresponding selection of its surfaces—as optical surfaces—, the fiber-optic waveguide may be used for the further modification of the light distribution.
According to another preferred embodiment of the invention, the fiber-optic waveguide has a light coupling-in point with a second light source on the input side, for the reflecting-in of light.
When the daytime driving light is switched off, the fiber-optic waveguide can, therefore, be used as signalling light in a manner known per se. As a result, a dual function of the headlight may be achieved in a simple manner.
According to another preferred embodiment of the invention, the fiber-optic waveguide is constructed as a first light decoupling element, which changes into a second light decoupling element of an adjacent headlight. In this case, the light decoupling element is constructed such that a portion of the light coupled into the first light decoupling element may be decoupled by way of the second light decoupling element. A second light decoupling element of an adjacent headlight can thereby be supplied with a light current by way of the first light decoupling element.
According to another embodiment of the invention, the light emitted by the fiber-optic waveguide may be used as a parking light or position light by dimming the light source. As a result of the dimming, a dual function of the headlight may therefore also be achieved in a simple manner.
According to another preferred embodiment of the invention, the area enclosed by the fiber-optic waveguide may be used for additional light functions. By means of the utilization of the central area, another light function can be achieved in a space-saving manner.
According to another preferred embodiment of the invention, the light source has a first light element, such as a helix or a filament as part of the light element, at the first focal point, for generating the light to be coupled into the fiber-optic waveguide, and a second light element, also such as a helix or a filament as part of the light element disposed in front of the first light element in the beaming direction, for generating light for another light function. In this case, a lens for the additional light function can be arranged in the area enclosed by the fiber-optic waveguide. The light of the second light element can be beamed directly into the lens. The use of a light source with two light elements results in an additional cost reduction and simplifies the lamp exchange. The reflector construction can thereby also be simplified. If required, it is also contemplated to shield the second light element toward the reflector or toward the first light element, or to arrange two separate light sources or lamps behind one another which, if required, are fastened on a common lamp carrier. As a result, special lamps would be avoided.
According to another preferred embodiment of the invention, the lens is constructed and/or arranged with respect to the second light element such that it generates a laterally deflected cornering light. Particularly when the lens axis is offset with respect to the headlight axis and/or contains prisms on the lens surface, a superimposable cornering light/turn light can be generated in a simple and cost-effective manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.